Which of the following is a biotic factor?

• A. A non-living factor such as air
• B. A measure of temperature
• C. A factor that influences ecosystems but is not living
• D. A living factor, such as plants and animals

Answer: (D)

Biotic factors are the living parts of an ecosystem—the organisms that grow, reproduce, and interact. A living factor like plants and animals fits this because it represents life within the environment and the relationships among organisms. The other options describe non-living elements: air is not living, temperature is a non-living measure, and a factor that influences ecosystems but is not living refers to abiotic influences. So, a living factor such as plants and animals is the biotic factor.